Chemocatalytic routes for the production of α-hydroxy carboxylic acids (e.g. lactic acid, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and glycolic acid) from biomass-derived sugars have been extensively studied in the recent years, as these acids, their esters, and lactones have been recognized to hold large potential as renewable, green platform chemicals for a number of industries (e.g. polymers, solvents, and fine chemicals).
Considerable progress has been made on the production of lactic acid and alkyl-lactates from trioses (glyceraldehyde (GLA) and dihydroxyacetone (DHA)), with nearly quantitative yields achievable with the state-of the art catalysts (e.g. tin containing zeotypes Sn-Beta and Sn-MFI, which catalyze 1,2 intramolecular hydride shift (1,2-HS) reactions) at moderate temperatures (ca. 100° C.) (FIG. 1). Similarly, the C4- and C2-products, 2-hydroxy-3-butenoic acid, 2,4-dihydroxybutanoic acid, and glycolic acid or their esters and/or lactones can be obtained in good yields when tetroses (erythrose, threose, and erythrulose), glycolaldehyde, or glyoxal are used as substrates (FIG. 2). However, the substrates required for these reactions are not easily obtained or isolated from biomass, as majority of terrestrial biomass comprises cellulose and hemicellulose (polymers of hexoses and pentoses).